Say your house is full of baby gear you got when Junior was a newborn. Your options are few: Craigslist, a yard sale, the Salvation Army.

Two young entrepreneurs in Mountain View want to add a word to that menu: Listia.

Gee Chuang and James Fong founded the startup in 2009 as an online community for people to unload unwanted stuff by trading it in for other people’s castoffs. Think of it as eBay (EBAY) meets the neighborhood swap meet.

On Tuesday, the company will announce a $1.75 million funding round led by heavy hitters including Andreessen Horowitz, Ron Conway’s SV Angel and PayPal co-founder Max Levchin. Chuang and Fong also will roll out a new iPhone version of the software they hope will turbocharge Listia’s growth.

Even without the app, Chuang and Fong say the site has been adding a couple thousand users a day, though they won’t divulge precise numbers.

The 31-year-olds met at Cornell University before moving to Silicon Valley a few years back. Fong worked at Sun Microsystems and Micron Technology, while Chuang toiled for a startup. On the side, they launched a couple of websites, including a shopping search engine for car parts and a site to let shoe shoppers compare prices and ratings.

Then came the day Fong went looking to unload a pair of gently used snowboarding boots. First he tried an online auction site, but “nobody wanted them, and I lost a chunk of fees. We figured there had to be a better solution.”

That solution ended up being a “virtual currency” that Listia users can acquire by putting things up for auction. They can use the same currency to buy other stuff. They incubated the idea as part of Mountain View’s Y Combinator, then quickly landed $400,000 from angel investors after showing off a product demo.

At any given time, Listia users offer tens of thousands of items for auction. Collectibles tend to be popular, as do DVDs, CDs and used clothing. Users are also free to offer new stuff for sale; handmade jewelry, for instance, is a growing category.

Tyhana Judd of Portland, Ore., has been using the site since the day it launched in August 2009. Piqued by a mention in a blog item, she thought Listia would offer a good way to unload some unwanted books. Now, she says, she visits the site several times a day — mostly unloading and picking up video games and movies.

Her proudest score: an original Sony PlayStation.

“It really is a thrill,” the 24-year-old said of the bidding process. “The hardest part is waiting for the stuff I win to show up in the mail.”

Listia makes money by offering users the chance to buy additional credits at 10 cents a pop if they haven’t banked enough via swaps to buy the items they want. Fong and Chuang are also experimenting with sponsored listings that users can pay to have their goods presented more prominently, as well as letting companies like Microsoft offer free items on the site as a form of advertising.

But, says Chuang, the site aims to be more than just a commerce platform. By letting users become “fans” of one another and acquire virtual “badges” for transactions, he and Fong have tried to bake in elements of gaming and social networks.

Says David Lee, managing member of SV Angel: “We invested in Listia because the founders did an awesome job of building and cultivating a community, which is very hard to do.”

Chuang says the new iPhone app is “something our users had been wanting for a long time.” With a built-in GPS function, the app will let users more easily home in on items close to them, avoiding shipping charges. Users won’t have to hover near their computers to be alerted if they’re outbid for a given item. And, Fong says, “We imagine people walking around the garage and snapping photos of everything they don’t need,” then uploading those images to Listia.

Part of the new funding will enable a roll-out to the Android platform, which Chuang and Fong hope to do before the end of the year. They’re also looking to Andreessen Horowitz in particular for guidance on expanding the business and recruiting; Listia just added its fifth employee and is looking to hire more engineers and software designers.

Chuang and Fong figure the money will see the company through the next year to 18 months, but there’s likely to be plenty more if they need it, given the enthusiasm for social-mobile startups. Says Chuang: “The atmosphere is great right now.”

Contact Peter Delevett at 408-271-3638. Follow him at Twitter.com/mercwiretap.

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